Toning examples... how, why....what?

My understanding is that cabinet toning is a fairly subtle, grey to brownish toning that a coin acquires over years of storage in a cabinet. The toning is caused by the wood vapors that mix in the air, making the coins darken evenly over time.

The silver dollar is quite gaudy. I don't know if it is the photograph, but it looks artificial to me - just to bright and splotchy. Now some silver dollars did acquire multiple color toning after storage in canvas bags. Perhaps that is the case with the silver dollar, I don't know.

All metals, except gold (pure gold, that is), oxidize over time, including this 50 reales from Segovia, 1635, which has acquired a nice grey and brown tone to both sides - a beauty - long may she reign.

 

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Actually the sulphur odor diminishes with time. My experience with liver of sulphur is that it creates dark brown to black toning, depending on the concentration. Using this chemical requires a very cautious approach.

 

Morgans are quite a bit different than most other coins and tend to have some of the most vivid examples of toning. Environment and storage methods help explain how the colors form. Many never reach the monster colors (especially if they were used in commerce). Some of the famous toned examples were kept for many years in canvas bags inside of bank vaults and treated with sulfur.

Here is a link to a great guide on toned Morgans:
http://www.jhonecash.com/coins/tonedmorgans.asp

 

That rainbow toned Morgan Dollar is a quintessential example of a bag toned Morgan and is absolutely naturally toned. If you are interested in the science behind it, please refer to @Morgandude11 post above or the link below written by Jason Poe.

What You Need to Know About: The Science of Toning

While we are on the subject of natural vs artificial toning, all of the coins shown in this post are artificially toned with the application of sulfur and heat.

 

My Hadrian Tridrachm is the weirdest toned silver I have ever seen with it's gold/copper look. Hadrian, Cilicia Aegaea, circa 117 AD. AR Tridrachm 9.6 gm, GIC 1218. Toned.

 

This is usually the case, but not always. Some patinas, especially light bluish-green patinas, can sometimes be very fragile and easily chipped off. This type of patina seems to me more common on provincial coins than imperial. I'm not sure why this is--possibly local environmental conditions, or perhaps it has something to do with the chemistry of orichalcum vs. bronze.
Here's an example from my collection. Had this coin retained all its original patina, it would be quite a beauty. Notice that where the patina has broken off, much of the fine detail has been lost along with it:

Marcus Aurelius
Caesar, A.D. 139-161
Augustus, A.D. 161-180
Provincial Bronze (AE26)
Moesia Inferior, Nikopolis ad Istrum, before A.D. 161
Obv: AVPHΛIOC OVHPOC KAICAP
Rev: NEIKOΠOΛEITΩNΠPOC IC - Serapis, standing left, holding scepter and sacrificing with patera over altar.
Unlisted in Moushmov or RPC; unpublished?
26mm, 11.0g.

 

The rainbow toning comes from contact with sulfur. A lot of the canvas bank bags, Wayte Raymond holders contained sulfur. It forms a thin film appearance on the surface of the coin. The refraction of light is what our eyes perceive as color

 

And then, as we know, there are certain sellers who apply blue toning to their coins artificially -- a color that, on the coin I bought, disappeared all by itself in a couple of months. Thankfully, because I never liked it to begin with. See my thread on my experience at https://www.cointalk.com/threads/a-mysterious-transformation.360216/

 

Natural old cabinet tone is especially valued by high end ancients collectors because they are a signal of old provenance, which is very important for the freedom to transfer coins across borders, donate to museums etc, and to resell for much higher prices. The tone doesn't directly indicate provenance but indicates a coin where one might reasonably expect to find a provenance within a year or so of exhaustive research. Specialists know very well the difference between natural old toning, and artificial. Natural toning in combination with decades or centuries of wear results in tiny but important variations in toning between more and less exposed areas of a coin. Sometimes one sees evidence of a coin being displayed obverse side up in a tray. So I have to disagree with those who say you can easily artificially tone a coin. You can, but not to deceive me

 

Actually many U.S. coins have colorful "rainbow" toning. Many are naturally toned and many are not.

Ancient coins are found toned. So far, the main colors I've seen on naturally toned silver ancients are iridescent blue and violet. I have not seen red, orange, green, or yellow. Nevertheless, silver alloys and methods of storage have changed so I'll bet these colors exist on naturally toned ancients, just rare. My beautifully toned ancient coins became toned while stored for decades in velvet lined little cases.

EDIT: I see a coin above has traces of red. I'm thinking of much more coverage by using "not seen."

PS I'll guarantee ancients exist with "modern applied color." Heat is one method. Add a little chemistry and...

 

Cabinet toning.


Ancient fouree of Nerva

Natural toning

To be fair, a more natural photo is more silver and blue and the gold is less obvious.

You can paint on toning very cheaply with stuff available on ebay. On ancients, I am very wary of deeply toned coins, and I am a sucker for toning.

 

DonnaML, posted: "And then, as we know, there are certain sellers who apply blue toning to their coins artificially -- a color that, on the coin I bought, disappeared all by itself in a couple of months. Thankfully, because I never liked it to begin with. See my thread on my experience at https://www.cointalk.com/threads/a-mysterious-transformation.360216/"

The link says you put it into a tray with a solution and that removed the color. IMHO, that does not qualify as "disappeared all by itself."

 

If you read what I actually said, and look at the actual photos I posted, you'll see that about 98% of the blue color did "disappear all by itself" before I put it in the solution to try to get rid of the little that remained. If you're going to nitpick with people, at least try to do so when it's justified.

 

Interesting coin.

Patina is basically a chemical alteration of a coin's surface. With bronze the oxidation process alters the copper into an oxide, usually malachite, but also cuprite and in rare instances azurite. This is process gives us the greens, browns, blues and combinations thereof.

So, the removal or loss of patina, such as with your coin, does result in the loss of detail in areas because some of the coin is gone. That's why it is a challenge to clean a coin in a manner that does not irreparably damage it.

 

There's two types of toning. Accretions which (potentially attractively) obscure the coin's surface and that which forms from a chemical reaction with the coin's metal. Most ancients that have any toning will have a combination.

That rainbow toning is a subset and can happen in both cases. You could apply a thin coating of a translucent material or, for a bigger challenge, you can induce oxidation. The color shifting is determined by the thickness of the layer. Depending on what the layer is made of it reflects or absorbs all light except for a very narrow range of the visual spectrum. However, it's not just the thickness. You also need an underlying layer that is reflective. This is why it's much more commonly seen in silver than in copper since ancient copper will have non-reflective patinas in pretty much every case unless stripped. It also explains why you don't see it naturally in gold since this metal does not oxidize.

Rasiel

 

Oh what a difference two years can make.

September 2018:


September 2020: